This invention relates to a valve for controlling the flow of solids and, more particularly, to a valve for controlling the removal of nuclear waste product.
There are many problems associated with controlling the flow of bulk solids. Flow conditions must take into account safety precautions, particle size variations, and the tendency of the particles to form agglomerates and clinkers. Industries such as grain and fertilizer use various systems involving conveyors and pumps to control the flow of their products. Such systems are entirely unacceptable for the removal of nuclear waste product. Nuclear waste product is typically produced from a high-temperature environment (550.degree. C.) over a relatively high pressure differential (20 inches water column). Also, nuclear waste product comes in a wide particle size distribution and is often subject to the formation of small clinkers and agglomerates. Such hazardous conditions mandate a safe, sealed, controllable removal system.
Frequently, nuclear waste product is removed from a fluidized bed. Non-nuclear fluidized bed applications typically control solids discharge with various mechanical valves. Mechanical valves are subject to frequent destruction when used with nuclear waste product.
Cyclone solids return seals apply various overflow type discharge valves. These valves are designed to treat the solids as a fluid and to discharge the solids as quickly as possible. The consistency of nuclear waste product is quite different from the solids flowing through cyclones. As stated earlier, there is great tendency to form agglomerates and clinkers which inhibits the flowability of the waste product. Furthermore, due to the radioactive nature of the product, its flow must be carefully controlled and metered.
Previous systems for controlling nuclear waste product removal involved the use of a product removal nozzle. This nozzle consists of a small diameter high velocity horizontal section (pipe) followed by a larger diameter horizontal deceleration section, which decelerates the solids to reduce erosion before they hit a blinded tee bend at the end of the section. A small diameter bar was welded across the nozzle inlet to prevent entry of lumps that might plug the nozzle. Dilution air was introduced near the nozzle entry to prevent plugging in the inlet section. This particular system was susceptible to frequent downtime as a result of plugging due to clinkers and agglomerates.
Therefore, it is an object of this invention to provide a valve for controlling the flow of solids.
It is another object of this invention to provide a safe, reliable device for metering the removal of nuclear waste product.
It is also an object of this invention to provide a valve for controlling the removal of solids that is operable in extreme temperature and pressure conditions.
It is a further object of this invention to provide a valve for controlling the removal of a nuclear waste product that is not susceptible to plugging by clinkers and agglomerates and that will remove product containing a wide particle size distribution.
Additional objects, advantages and novel features of the invention will be set forth in part of the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.